Colorado considering defunct oil, gas wells as carbon stores
DENVER — From Colorado’s high desert to the wooded hills of Pennsylvania, millions of oil and gas wells sit deserted, plunging thousands of feet into the earth.
Many of these wells haven’t been plugged. Some of them leak greenhouse gases.
In Colorado, lawmakers are considering a solution that would give these wells a new purpose: deep receptacles to trap carbon for millennia.
The idea is to keep carbon locked away in a special type of charcoal known as biochar — made by burning organic matter at high heat and low oxygen. The substance could be used to fill defunct oil and gas wells.
Proponents say biochar would not only filter dangerous gas leaks but also stop that carbon from forming carbon dioxide, a greenhouse gas.
Last week, Colorado lawmakers approved a study to assess if biochar would work to plug orphaned wells.
If successful, experts say that sinking biochar into a portion of the over 3 million abandoned oil wells nationwide could help tackle climate change — estimates range from keeping millions to billions of tons of carbon dioxide out of the atmosphere.
Still, the idea is relatively new and a number of feasibility questions remain.
Carbon naturally cycles through Earth’s ecosystems, floating in the atmosphere as carbon dioxide before being snatched up by little bluestem grasses, ingested by grazing bison on the prairie, and when the animal keels over and begins decomposing, returning to the atmosphere as carbon dioxide.
But extracting fossil fuels has unearthed carbon — formed out of ancient plant matter over eons — that’s been stored underground largely since the Mesozoic Era more than 65 million years ago.
North of Denver in the small town of Berthoud, Colorado, one company already makes biochar. On a recent day at Biochar Now’s facility, a tractor drove across the muddy yard, its bucket holding shards of wood bound for a new life as biochar. Nearby, dead logs were stacked in piles.
What they have in common, said James Gaspard, the company’s co-founder, is that they’d otherwise be doomed to rot or burn, releasing carbon dioxide. Instead, the wood debris is loaded into large kilns, where the heat burns at three times the temperature of fire and the oxygen is sucked from the chamber in a process called pyrolysis. What’s left behind is biochar.
The substance has a carbon structure closer to a diamond, said Jim Ippolito, a Colorado State University professor. While diamonds might last forever, biochar isn’t far behind and can keep the carbon inert — unable to form carbon dioxide — for centuries if not millennia.
Unlike a decomposing bison, biochar pulls carbon out of the earth’s carbon cycle. That’s partly why it’s being proposed to plug oil and gas wells. It could help absorb dangerous gases such as methane that seep from abandoned shafts.